Seems like a really good idea. But the security would have to be so tight so people don't lose their coins.
There is actually no risk of losing your Coins by using Coinlend since the API keys we need to automate the margin funding, does not require withdrawal permission. Check out our FAQ for more information:
https://coinlend.org/#!FAQ
Nevertheless, security is very important for us to protect the user data and therefore everything at Coinlend is encrypted via SSL, API credentials are stored encrypted and we offer 2FA!